WASHINGTON AND ST. LOUIS
— It's a vision that seems almost too good to be true: Electric cars that wouldn't ever need a plug-in recharge.

Yet such is the promise of fuel-cell technology. Proponents have long held that these futuristic sort-of-battery devices are the world's best hope for replacing the noisy, inefficient, dirty internal combustion engine.

The Bush administration, in fact, has decided that US government support for the development of environmentally friendly vehicles should now focus much more on fuel-cell work. Secretary of Energy Spencer Abraham announced the shift yesterday during a speech at the auto show in Detroit.

Fuel-cell cars are still a long way from commercial viability. A few years ago, electric vehicles were the subject of similar hype - and they're not exactly rivals of V-6 SUVs today. If nothing else, developing a network of refueling stations for hydrogen-based fuel-cell power units could take a decade or more.

"I see [fuel cells] as a long-term plan," says Richard DeBlasio, technical manager for distributed power at the National Renewable Energy Laboratory in Golden, Colo. "It will take years to develop the infrastructure."

Fuel cells were first developed to provide a source of power for the satellites and manned capsules of the US space program.

The concept behind fuel cells is a powerful one: Instead of burning carbon in the form of trees and coal and oil, as the world has done since before the Industrial Revolution, it could consume hydrogen, the most common element in the universe.

Fuel cells produce electricity via an electrochemical process that combines hydrogen with oxygen from the air. The hydrogen can come from traditional fossil fuels, such as natural gas, or even from renewable sources such as methane from garbage dumps.

There are many different types of fuel cells, but those considered most promising for cars and trucks are a lightweight style that uses a thin polymer membrane (instead of some sort of liquid solution) as the electrolyte that helps the electrochemical power process along.

Fuel cells have no moving parts. Their only emission is water vapor. They are far more efficient than internal-combustion engines, which convert only about 15 percent of the energy inherent in gasoline into forward motion. A stack of fuel cells capable of powering a car or truck can be made small enough to run in a tunnel under a typical chassis, leaving a hump similar to that of an automatic transmission.

They don't have to sit at a recharging station for hours, as do current electric cars. Refueling would be a simple, quick liquid or gas transfer, similar to today's gas-and-go.

No noise. No greenhouse gases. No smog. No inexplicable oil-spattered bulbous shape under the hood. What's not to like here? "We're on the cusp of a brand-new era ... from a mechanical-combustion era to an electrochemical [era]," says Jim Ohi, leader of the hydrogen and natural-gas systems at the National Renewable Energy Laboratory.

Of course, the world has been on the cusp of lots of eras that never quite arrived. Remember videophones? Scientists have said they were just around the corner since about 1960. Nuclear power was once going to provide power too cheap to meter. Even the promise of fully electric battery cars has dimmed, as consumers proved unenthusiastic about tiny cars that need a night's recharge before being able to reach top speed of two miles per hour.

Cost is one big obstacle facing fuel cells. To compete directly with the internal-combustion engine, their price will have to fall to about $50 per kilowatt, says Mr. Ohi. Current systems cost 90 times that amount.

Converting the vast consumer auto infrastructure to handle hydrogen cars would be another problem. Modifying a gas station to pump hydrogen fuel could cost $70,000 or more. Government support is crucial if these obstacles are to be overcome, say proponents. That's where the Bush administration may come in.

Bush officials have announced that they want to end US involvement in the $1.5 billion government-private partnership intended to develop high-mileage traditional gasoline vehicles. Launched with great fanfare by the Clinton administration, the effort has produced some valuable technologies, but is still short of its goal of a commercially-viable 80 MPG family sedan.

As yet there is no price tag on the new fuel-cell effort, but the Clinton-era program it would replace was slated to receive about $130 million this year. Critics say that the Bush administration simply wants to end pressure on auto companies to make their vehicles more fuel-efficient in the short term, in return for a vague promise of future environmental nirvana.